ANTAKYA, Turkey — The rebel commander was nervous. He had changed phone numbers and been difficult to reach before finally agreeing to meet in Antakya, a city near the border with war-torn Syria that has long swarmed with rebels, refugees, and spies. On the road to an out-of-the-way hotel, he told the driver to avoid the main route through town. “It’s better not to drive among all the people,” he said.

It was an open secret that the commander had once received cash and weapons from the CIA, part of a covert U.S. program that backs rebel groups against both ISIS and the Syrian government of Bashar al-Assad.

When his battalion was eventually driven from Syria by its jihadi rivals, like a number of U.S.-backed groups, he pleaded with his U.S. handlers for better support, but it wasn’t enough. So he was, he said, “out of the game.”

Now, he said, sitting at a quiet table at the hotel, he had received an offer that could bring him back in — and potentially make him even stronger than before.

He was being recruited, he said, to work for the U.S.’s rival in Syria: Russia.

“They told me, ‘We will support you forever. We won’t leave you on your own like your old friends did,’” he said. “Honestly, I’m still thinking about it.”

“They told me, ‘We will support you forever. We won’t leave you on your own like your old friends did.’”

The commander said that five years into a war that has killed some 400,000 people and created nearly 5 million refugees, Russia is recruiting current and former U.S. allies to its side. His revelation was confirmed by four people who said they, too, had been approached with offers from Russia and by two Syrian middlemen who said they delivered them.

The moves come as Russia ratchets up its involvement in Syria with troops and airstrikes. Russia says its military campaign is designed to target ISIS — in reality it has targeted all rebels, including some who are stillbacked by the U.S., while also wreaking havoc on civilians.

The secret outreach shows that as it works to muscle the U.S. out of Syria, Russia isn’t just bombing the U.S.’s current and former rebel allies — it’s also working to co-opt them, launching a shadowy campaign that seeks to highlight U.S. weakness in Syria. Ultimately, Russia could be hoping to help Assad win the war by dividing the opposition, driving a wedge between rebel groups and their traditional backers, and getting them to turn their guns on his enemies.

The commander said he found Russia’s offer appealing. Delivered by a Syrian agent who met him first in Antakya and then inside Syria, he said, the offer was this: Choose a rebel-held area in northern Syria and head there with his men, many of whom were trained as part of the CIA program. Russia would protect him — “from any group” and “any country” — with airstrikes, which he could personally call in. And it would give him all the money and weapons he would need.

In return, he would help to spearhead the fight against both ISIS and Jabhat al-Nusra, the al-Qaeda affiliate in Syria that is one of the most potent forces battling the regime. Once the extremists were defeated, the commander, along with other rebel leaders who had come on board, would negotiate with the regime first to end the war and then to decide Assad’s fate.

Left unsaid was the fact that, in the meantime, Russia and the regime would continue working to wipe out anyone who opposed them.

This plan — whatever its chances of succeeding — represents an ideal outcome for Russia in Syria, preserving its influence in a country it considers an important client state while dividing the rebels and helping the regime to a military victory.

It would also mean a triumph over U.S. foreign policy. The Obama administration has publicly insisted for years, in concert with the opposition, that Assad must step down before the war can end — however, its allies have long criticized it for not doing enough to make that happen.

Having a former proxy switch sides to Russia, the commander knew, could anger the U.S. and its ally Turkey, which works with the U.S. to support rebels across its border. This notion fueled his paranoia — and at the hotel, he glanced nervously over his shoulder when other patrons walked by. He requested anonymity to reveal the details of a secret courtship still underway. “If I say yes, I will create a new enemy in the U.S. or Turkey,” he said.

Years of failed U.S. partnerships have left a long trail of angry rebels, and the commander suspected that there were others being tempted: “Russian intelligence knows all the groups who were fighting ISIS and dealing with the U.S. and not getting enough support.”

The four additional rebel leaders, all with current or past U.S. ties, said they had also been approached with similar offers, either via Russian officials or Syrian middlemen.

One of Moscow’s main aims, each of them said, was to outmaneuver the U.S. “Their goal is to take control in Syria and kick America out,” one of these rebel leaders said, requesting anonymity to protect his reputation and because he still works with the U.S.

He said he had traveled to Egypt to speak with Russian officials but declined their offer. It included the chance to be part of a military council with the regime along with “money, bullets, weapons, and all that I ask,” he said. “But if I put my hand in theirs it means I will destroy the revolution and the Syrian people along with it.”

The Russian foreign ministry directed requests for comment to the Russian defense ministry, which did not respond.

Louay al-Hussein, a prominent politician who was a member of the regime-sanctioned opposition before fleeing Syria last year, said he had relayed offers of air support, cash, and arms to rebels from officials at “more than one” Russian embassy. “They want to win in Syria against the international countries [backing the opposition], including the U.S.,” he said of Russia. “Moscow wants to find a political solution — but first they want to win.”

Of his own motivation, he added, “I just want to stop the war.”

Russia’s intervention came at a time when the regime seemed in danger of losing, and it has regained the momentum for Assad. Hussein said he thought this gave Moscow leverage to force a potential political solution on the Syrian dictator. “The regime is now just a militia. It is no longer a political regime,” he said. “We don’t care what the regime says anymore — only what Russia says. They are the leaders in Syria right now.”

Another opposition politician who said he had acted as an intermediary, Anas al-Shamy, said that Russia had been working with “some groups that broke away from the Americans,” though he declined to name them. “This information is secret,” he said.

Spokespeople for the U.S. State Department, the CIA, and the Obama administration’s National Security Council declined to comment.

An official with another government that backs the Syrian opposition said he believed the U.S. was aware of the Russian outreach. “If I heard about it and you heard about it, you can bet the Americans also heard about it,” he said, speaking on condition of anonymity because he wasn’t authorized to discuss the subject. “This is a turf war.”

Russia's tactic suggests that Moscow sees an opening to assert greater influence in Syria and undermine the U.S. along the way.

“I think the U.S. is less and less of an influential player in the civil war,” said Robert S. Ford, a senior fellow at the Middle East Institute in Washington and U.S. ambassador to Syria from 2011 to 2014.

Ford played a key role in the last round of peace talks in Geneva, in March 2014, which were sponsored by the U.S. and Russia and ended without a deal. A new peace process that has been underway since the spring again looks on the verge of collapse, with Assad declaring on Tuesday that it had “failed,” vowing to take back “every inch” of the country.

Washington’s leverage in the talks has been limited, Ford said, as Russia steps up its involvement on the ground while the U.S. steps back. “They’ve pretty much ceded to Russian military action,” he said. “If the Americans wanted to reassert themselves in the process they would have [increased] arms supplies and encouraged the Turks and Saudis to do the same, but as far as I can tell they haven’t.”

“The Americans are showing the Russians that they are weak in Syria and not invested.”

Yet Ford added that Russia’s outreach to rebels also betrays its own weakness. “What it tells me is that the Russians don’t have an exit strategy from Syria, and they’re trying to find one,” he said. “And I think they understand that if they don’t win over some element of the moderate opposition, they’re not going to be able to get a political exit very easily.”

He added: “The Syrian war at this point has such a variety of groups and governments operating in it that there’s really not one country that can control where it’s going. I have the sense that the Russians are finding this much harder than they expected.”

Many of its Syrian allies say the Obama administration, seven months from leaving office, is only going through the motions in its efforts to end the war, and perhaps is even happy to let Moscow take charge. “The Americans are showing the Russians that they are weak in Syria and not invested,” said Obadah al-Kaddri, a Syrian politician working with the opposition’s U.S.-backed negotiating team in Geneva. “The U.S. aim is just to get the opposition to go to Geneva so they can go back and tell the American people and Congress that they tried.”

Kaddri traveled to Moscow for his own meetings with Russian officials this spring, hoping to broker an understanding between rebel groups and the Russian government. The Russians told him they had no love for Assad, he said, but wanted to keep Syria from disintegrating. He also recalled them saying that their attacks on moderate rebels had been cases of mistaken identity, pulling out a map and inviting him to show them where his rebel friends were based. He decided, in the end, that “the Russians are lying.”

Rebels should be wary of the Russian outreach, said Frederic C. Hof, a senior fellow at the Atlantic Council and former adviser to the Obama administration on Syria. “Russia has a track record, and if I were one of these rebel commanders, that track record would neutralize some of the sweet talk coming from the lips of a Russian operative,” he said. “The Russians have used Jabhat al-Nusra as an excuse for bombing anything they please. And they’ve not been shy about committing war crimes.”

Hof added that Russia may be more tied to Assad than its offers to rebels suggest. “[Russian President Vladimir] Putin sees Syria as a place where the alleged U.S. program of democratic regime change can be defeated decisively, and that is what he is selling to the Russian people,” he said. “Assad is his poster boy. He personifies the Syrian state that Putin says he’s going to save. Assad serves a purpose for Putin, and Assad knows it.”

Some rebels with U.S. ties confirmed they had been approached by Russia but said they had rejected the Russian outreach out of hand.

“The U.S. is supporting us and we are working for American intelligence,” said one rebel official who worked closely with the U.S. when his battalion was part of the CIA program, and requested anonymity due to security concerns. “How can we cheat American intelligence and start working for the Russians?”

“I would never do it. I would never sell my revolution,” said Abdullah Awdah, who was the military commander for Harakat Hazm, one of the most powerful U.S.-backed groups in Syria until it was driven from the country by extremists last year.

His U.S. contacts were aware of the Russian outreach, Awdah added. “We are in touch with Americans here, maybe directly or not directly, and they are upset with this [outreach],” he said. “We are just like a piece of paper, being passed between the big countries who are playing in Syria.”

Other rebel leaders were receptive at least to hearing the Russians out.

“We are just like a piece of paper, being passed between the big countries who are playing in Syria.”

Mousa Humaidi, a 40-year-old ex-businessman from northern Syria, was a senior leader with the Syrian Revolutionaries Front, or SRF, and personally received many of the weapons shipments, including TOW anti-tank missiles, the U.S. sent the group in Syria, he said. The SRF was routed by Jabhat al-Nusra in late 2014 — and soon after, he said, he was approached by Russia via Syrian middlemen including the opposition politician Hussein. “Honestly I found that they are honest and good friends, because they support their friends,” he said. “Russia has more honor than America.”

Humaidi said he declined the offer, in part thanks to Russia’s attacks on moderate rebels and civilians. But he suggested that a seasoned commander could navigate the contours of a deal. Had he accepted, he said, he would have arranged for soldiers still loyal to him, who are currently being armed and trained by the the U.S., to cross into Syria from Turkey and defect. And he was confident he could have rallied his men to the cause. “I could do it if I wanted. I have my ways,” he said. “I was living with my fighters in Syria and I know how they think, what they want, and how to make them agree.”

At the hotel in Antakya, the commander was still weighing his options.

He and the Syrian agent had met first in Turkey and then in Syria, he said, where the man told him Russian jets were protecting them. When he said he needed time to think, he added, the man handed him $100,000.

On his phone were voice messages from the same Syrian agent, he said; the last one was six days old. “We want you, we want you,” a voice said in Arabic. “Go, my brother — we closed the old page. You go in person and manage the work.”

The commander knew that joining forces with Russia would mean a personal concession that the regime had won. On the other hand, he reasoned, Russia was at least offering, in contrast to the U.S., a way for the bloodshed to come to an end. “The Americans just want to buy time,” he said. “But the Russians are here to work.”

He headed back to the car, lost in thought. “I cannot decide,” he said. “It’s like walking down a dark tunnel, and you don’t know if you will find the light.”

With additional reporting by Munzer al-Awad from Istanbul and Antakya.